The U.S. Navy has performed considerable research in manned and unmanned deep submersibles for salvage, reconnaissance, and surveillance work. One of the plausible methods for changing the buoyancy of these submersibles has been the utilization of various generated gases. One gas which has shown promise is hydrazine which is stored in liquid form and converted to a gas over a catalyst bed for increasing the buoyancy of the submersible.
In the utilization of a specific gas as well as the design of the submersible it has become necessary to ascertain the degree of buoyancy achieved from various gas sources at various ocean depths. The most practical way of accomplishing such a test is to perform it at the desired ocean depth. A gas generation device, such as a hydrazine generator, generates the gas which is transferred to a load cell. The load cell is utilized for indicating the degree of buoyancy achieved at the specified depth.
The prior art offers very little in the way of a load cell which can be utilized at an ocean depth for determining the buoyancy achieved from generated gases. One method investigated was a collapsible bag for containing the buoyancy gases wherein the bag is connected to a spring system for scribing the buoyancy increase on a piece of plexiglass. This combination did not have adequate sensitivity due to the friction effects of the springs and the scribe. It was found that friction is the biggest problem to overcome in providing an adequate buoyancy indicator. Subsequently, the scribe was replaced with a linear potentiometer, and again the friction of the springs prevented accurate measurement of the small changes in the buoyancy. Commercial load measuring devices include a "fish scale" type which has no capacity for direct recording of the measurement. Commercial hydraulic units are designed to weigh loads hanging from them in a homogenous gravity field. These devices are generally unsuitable for ocean measurements due to their high weight coupled with the fact that gravity acts downward on the cell components, which are generally heavy, while the buoyancy measurement is directed upward. Many of the commercial devices do not lend themselves to salt water immersion.